In exhaust emission control systems for internal combustion engines, there are some systems which promote catalytic reaction by supplying secondary air into exhaust manifolds or catalytic converters. On the other hand, fuel atomizers are employed for improving fuel economy and engine output performance. There are some atomizers which inject air from an air pump around fuel injection valves. The present invention relates to a method and a system for controlling an internal combustion engine with an air pump. More specifically, the invention relates to a driving of the air pump by means of a starter motor.
JP-A-1-253565 as unexamined publication for Japanese Patent Application filed on Apr. 4, 1988, discloses a system for atomizing fuel by injecting an air fed from an electric air pump to a fuel supplied into an intake manifold through one or more fuel injection valves.
Also, JU-A-2-107763 as unexamined publication for Japanese Utility Model Application filed on Feb. 15, 1989, discloses an air pump which is driven by a starter motor for cranking the internal combustion engine during cranking period and is driven by an engine revolution after starting-up of the engine.
In the field of the internal combustion engine, it have been known to supply the air by means of the electric motor which is driven by a sophisticated motor and to employ an air pump which is driven by a starter motor or the engine per se in place of the electric air pump.
However, when the electric air pump is employed, it may encounter a problem of an excessive load on a battery by driving of the electric air pump during cranking of the engine to make revolution of the starter motor unstable and to cause difficulty in starting up of the engine.
In contrast to this, in case of the air pump driven by the starter motor, an electrical and a mechanical loss can be reduced for elimination of the sophisticated motor for driving the air pump and the load on the battery can be reduced to make the revolution of the starter motor much stable.
On the other hand, since the starter motor is generally designed to be stopped once the engine is started up through cranking. Another source of power for driving the air pump becomes necessary after termination of driving of the starter motor.
It is possible to consider a revolution torque of the engine per se as another source of the power for driving the air pump. However, in such case, the power transmission path necessarily becomes complicate for necessity of switching between the starter motor and a rotary output shaft of the engine. Therefore, this solution cannot be practical.